osmux: Generate AMR OA payload paddings bits as 0

Some AMR format's payload size doesn't necessarily fit octet boundaries.
When AMR octet-aligned is used, padding bits are appended at the end to
fill the octet.
Until this patch, the padding bits where set with whatever payload fill
pattern was provided. Instead of doing so, better set the padding bits
to 0 to avoid conflicts when checking the received paytload later on,
since those bits are potentially be going to be set to 0 (eg when
converting to bandwidth-efficient).

Related: SYS#6161
Change-Id: I5bc68eb05c2f5500a259f4c73d14b51794f7f078
2 files changed